Tectonic evolution characteristics of Lishui Sag, East China Sea Shelf Basin

To detailly describe the tectonic evolution history of Lishui Sag of the East China Sea Shelf Basin, eight seismic sections from north to south were selected. The balanced section technology was used to restore structural evolution section, and some parameters such as extension amount, ratio and rate were measured. The extension characteristics of the sag during ten geological periods were described quantitatively and finely, moreover, the stage and spatial extension characteristics were also discussed. The structural evolution of the sag were classified into six stages: the initial, early and late stages of fault depression, the depression stage, the inversion stage and the stable subsidence stage. It was considered that the most intense stage for fault depression and fault activity in the sag was the deposition stage of the lower Lingfeng Formation (T₉⁰-T₈⁸), and the extension and contraction characteristics of different evolution stages were different in space. The tectonic evolution of the Lishui Sag, controlled by the geodynamic background of retrogressive subduction of the (paleo) Pacific plate to the Eurasian plate, reflects the rule of tectonic and sedimentary migration from west to east in the East China Sea Shelf Basin since the Late Mesozoic, and is closely related to the interaction of the convergence plates around the East China Sea shelf Basin.